This invention relates generally to paperboard containers and more particularly to an improved construction for a metal ring used to reinforce and protect the upper edge of a large paperboard container.
Cylindrical paperboard containers are used in a variety of packaging applications, including the packaging of foods. Relatively large diameter paperboard containers having a capacity of 3 gallons more or less are widely used to package food products in bulk quantities. The edges of these large containers are susceptible to being frayed and torn and are generally lacking in structural strength. Typically, a metal reinforcing ring is applied to the upper edge of the container to provide it with the necessary strength and protection.
The metal reinforcing rings that have been used in the past are applied to the container by crimping rolls which roll a rim portion of the ring over the top edge of the container. The ring is held in place on the container by an edge of the rolled rim which bites into the container wall. The ring extends along the inside surface of the container and terminates in a lower edge which lies against the inside surface of the container wall. Although this type of reinforcing ring functions well to strengthen and protect the edge of the container, it has not been entirely satisfactory in all respects. Perhaps most notably, the lower edge of the ring is an exposed edge which can cut the fingers and hands of persons reaching into the container. In addition, the manner in which the ring is fastened on the rim of the container is lacking somewhat in security, and this detracts from the structural integrity of the rim area of the container.
The present invention is directed to an improved reinforcing ring which is applied to the container in a manner to eliminate all exposed edges and other sharp or hazardous surfaces. The reinforcing ring is also held in place more securely than the rings that have been used in the past.
In accordance with the invention, a pair of crimping rolls act to crimp the reinforcing ring onto the upper edge of a paperboard container. The crimping rolls have specially formed shaping surfaces which roll the rim of the reinforcing ring over the container edge and press a band portion of the ring against the inside surface of a reduced diameter neck which is formed on the container by the crimping rolls. It is a particular feature of the invention that the shaping surfaces of the crimping rolls are arranged to curl a lip on the lower edge of the ring under and along a shoulder which extends between the neck and the main body of the container. The free edge of the curled lip is butted against the inside of the container wall where it is not exposed and is not susceptible to catching on or cutting the fingers or hands. A series of sharply pointed pins are carried on the inside crimping roll to form teeth on the band portion of the ring which bite into the container in opposition to the edge of the rolled rim in order to strengthen the connection between the reinforcing ring and the container.